In recent years, a material (separator membrane), which selectively separates helium gas from mixed gas containing helium gas having a small molecular diameter, and the selective separation method have been examined.
As the helium gas separator material, a separator membrane composed of a polymer is known. Patent Document 1 discloses a gas separator membrane composed of a carbon membrane containing silver or copper. Patent Document 2 discloses a polymeric gas separator membrane obtained by performing hydrolysis and polycondensation of a composition composed of a polyether copolymer having a specific structure and a polyfunctional alkoxysilane such as tetraalkoxysilane or trialkoxysilane. Furthermore, Patent Document 3 discloses a helium gas separator material including an α-alumina substrate that has communication holes, a silica membrane that covers the surface of the α-alumina substrate, and a silicon carbide membrane that comes into contact with the inside of the communication holes on the surface of the SiOC membrane.